This invention pertains generally to the art of radial keratotomy refractive eye surgery and in particular to a method and apparatus for making a plurality of radial incisions of predetermined length and depth simultaneously in the cornea of an eye.
Radial keratotomy is a surgical procedure for the correction of myopia or nearsightedness under which a series of radial incisions are made into the cornea of the eye. These incisions cause the peripheral portion of the cornea to bulge outward and, cause the central portion of the cornea to flatten, thus correcting the patient's vision.
The thickness, curvature and size of the cornea along with the degree of the nearsightedness and age and sex of the patient determine (i) the number of incisions to be made, (ii) the depth of the incisions, (iii) the length of the incisions and (iv) the size of the optical zone, i.e., the uncut central portion of the cornea. The procedure usually takes about fifteen to twenty minutes and requires four to sixteen incisions.
Heretofore, it has been conventional to make individual incisions sequentially, and by hand. Because of the amount of time required and the number of incisions involved, there are many problems associated with such current procedures. One problem is keeping the incisions properly straight and evenly spaced. During surgery, the cornea swells (thickens) and softens (e.g., because of the trauma involved), making the last few incisions much more difficult than earlier ones.
Additionally, the cornea is much thicker at the periphery than at the central or optical zone. Frequently, second cuts in the original incisions are required near the periphery of the cornea to obtain the desired depth of incision.
Still further, during the surgery care must also be taken to ensure that the incisions are not too long or too deep. The incisions should not be so long so as to extend into the sclera, the white part of the eye. The incisions also should not be so deep so as to extend through descemets membrane of the eye.
Moreover, when surgical incisions have to be made sequentially, by hand, there is always an attendant risk of non-uniformity or non-precision of incision, and this risk is magnified by the risk of softening of the cornea described above.
Others have tried various means to obviate some of these complications. For example, Villasenor, et al., U.S. Pat. No. 4,406,285, disclose a semispherical template with radial slots to ensure straight, evenly spaced incisions. Cutting depth is limited by varying the thickness of the template. However, a surgeon must still make each incision manually. Thus, the last incisions are still more difficult to make than earlier ones because the cornea will begin to thicken as additional cuts are made.